Development of a high-speed digital pulse signal acquisition and processing system based on MTCA for liquid scintillator neutron detector on EAST

In this experimental study, involving deuterium–deuterium fusion neutron emission spectroscopy measurement on the experimental advanced superconducting tokamak(EAST), a liquid scintillator detector(BC501 A) was employed. This decision was based on the detector's superior sensitivity, optimal time-response, and its exceptional n–γ discrimination capability. This detector emits fast pulse signals that are as narrow as 100 ns, with high count rates that can peak at several Mcps. However, conventional nuclear circuits faced challenges in performing pulse height analysis, n–γ pulse shape discrimination, and in recording the entire pulse waveform under such high count rate conditions. To address these challenges, a high-speed digital pulse signal acquisition and processing system was designed. The system was developed around a micro-telecommunications computing architecture. Within this structure, a signal acquisition and processing(SAQP) module communicated through PCI Express links, achieving a bandwidth of up to 1.6 GB/s. To accurately capture the detailed shape of the pulses, four channels of analog-to-digital converters were used, each with a 500-MSPS sampling rate and a 14-bit resolution, ensuring an accuracy that surpassed 11 bits. An n–γ discrimination algorithm, based on the two-gate integral method, was also developed. Implemented within field programmable gate arrays, this algorithm provided a real-time n–γ discrimination spectrum for pulse height analysis. The system underwent rigorous testing in a laboratory setting and during an EAST experiment. The results confirmed that the innovative SAQP system can satisfy the demanding requirements of high-parameter experiments, manage count rates of up to 2 Mcps, execute real-time n–γ discrimination algorithms, and record entire pulse waveforms without any data loss.

Analysis of droplet transfer of pulsed MIG welding based on electrical signal and high-speed photography

In order to study how welding parameters affect welding quality and droplet transfer, a synchronous acquisition and analysis system is established to acquire and analyze electrical signal and instantaneous images of droplet transfer simultaneously, which is based on a self-developed soft-switching inverter. On the one hand, welding current and voltage signals are acquired and analyzed by a self-developed dynamic wavelet analyzer. On the other hand, images are filtered and optimized after they are captured by high-speed camera. The results show that instantaneous waveforms and statistical data of electrical signal contribute to make an overall assessment of welding quality, and that optimized high-speed images allow a visual and clear observation of droplet transfer process. The analysis of both waveforms and images leads to a further research on droplet transfer mechanism and provides a basis for precise control of droplet transfer.

Electric characteristic and cavitation bubble dynamics using underwater pulsed discharge

Underwater pulsed discharge is widely applied in medicine, machining, and material modification.The induced cavitation bubble and subsequent cavitation collapse are considered the major motivations behind these applications. This paper presents an underwater pulsed discharge system.The experimental setup is established to induce and investigate the cavitation bubble assisted with a high-speed camera. Three aspects, including the characteristic of the discharge with different applied voltages and conductivities, the evolution of the cavitation bubble profile, and the energy efficiency of cavitation bubble inducing, are investigated, respectively. Especially, the mechanism of pre-discharge time delay in the low field intensity case is explained using the Joule heat effect.The results show the validity of the underwater pulsed discharger and experimental setup. The present underwater pulsed discharger is proved to be a simple, portable, and easy-to-implement device for the investigation of cavitation bubble dynamics.

Dynamic simulation and safety evaluation of high-speed trains meeting in open air

Dynamic responses of a carriage under excitation with the German high-speed low-interference track spectrum together with the air pressure pulse generated as high-speed trains passing each other are investigated with a multi-body dynamics method.The variations of degrees of freedom（DOFs：horizontal movement,roll angle,and yaw angle）,the lateral wheel-rail force,the derailment coefficient and the rate of wheel load reduction with time when two carriages meet in open air are obtained and compared with the results of a single train travelling at specifie speeds.Results show that the rate of wheel load reduction increases with the increase of train speed and meets some safety standard at a certain speed,but exceeding the value of the rate of wheel load reduction does not necessarily mean derailment.The evaluation standard of the rate of wheel load reduction is somewhat conservative and may be loosened.The pressure pulse has significan effects on the train DOFs,and the evaluations of these safety indexes are strongly suggested in practice.The pressure pulse has a limited effect on the derailment coefficien and the lateral wheel-rail force,and,thus,their further evaluations may be not necessary.

Experimental investigation on the plasma morphology of ablative pulsed plasma thruster with tongue-shaped and flared electrodes

Ablative pulsed plasma thrusters(APPTs)are considered as an attractive propulsion option for station-keeping and drag makeup purposes for mass-and power-limited satellites.In order to understand the physical mechanism of APPTs,high-speed camera and optical emission spectroscopy are utilized to investigate the plasma characteristics including the spatial distribution and composition between the electrodes.The plume images and spectra at different times and positions are experimentally recorded,and the spatial distribution,composition,and trajectory of plasmas can be concluded through analyzing them.With the increase of the distance from the ablation surface,two clusters of plasmas near the anode and cathode meet downstream,and the species and density of plasmas tend to be uniform.

Characteristic analysis of air pressure wave generated by high-speed trains traveling through a tunnel

It is a complicated dynamic phenomenon when a transient pressure pulse is triggered by two high-speed trains passing each other in a tunnel. The air pressure pulse is a transient excitation to side wall of the car body. It can stimulate almost all vibration modes of the car body and the correlated assemblies, cause serious aerodynamic noise, and have important impacts on car body distortion, train noise, and operation safety. This article analyzes the time- frequency characteristics and main parameters of field-measured the air pressure wave, and its relationship with the train velocity as well as the vibration of the car body. Cepstrum analysis concludes that in the process of the meeting, the air pressure wave in tunnel crossing is a multiplying pressure wave instead of a superposed wave. The pressure pulse during the meeting is non-symmetrical one featured with a sharp front, large amplitude, fluctuating central sec- tion, and less sharp tail. The pulse width is inversely proportional to the train speed. As the speed increases, the impulse amplitude is amplified, and the speed of pulse front is advanced.

基于模型熵处理的泥浆脉冲信号去噪方法研究

泥浆正脉冲传输技术在石油钻探中应用非常广泛,但泥浆正脉冲信号包含大量噪声,其中泵噪声为主要噪声来源,不仅时域上完全覆盖有用信号,而且频域上存在频谱混叠。在泵噪声特性的基础上,建立了一种泵噪声状态空间模型(线性时不变模型),引入最大相关熵准则去除泵噪声的野值,利用基于熵处理的标准卡尔曼滤波对泵噪声进行重构和滤波。此外,为实时处理信号的需求,采用随机共振原则滤除泵噪声后的剩余随机噪声。同时,模拟了稳态/非稳态泵噪声状态下几种不同信噪比的含噪泥浆正脉冲信号,分析评价方案的噪声抑制能力。结果表明,该方案能够抑制甚至去除原始信号中的稳态/非稳态泵噪声,可以将信号的信噪比提高约5~24 dB。

井下高速传输技术应用现状及前景展望

随着钻井智能化程度的不断提高,井下与地面的信息传输已成为钻井工程领域的重要研究课题,在随钻测量与控制中占有十分重要的地位。通过信息传输系统可以实时监测随钻信息及地质参数,进而可以对井下的执行机构进行实时调控。在此介绍了声波传输技术、电磁传输技术和泥浆脉冲传输技术的技术特征以及在国内外所取得的最新的仪器成果,同时阐述了各传输技术的未来发展趋势。

Motion detection for high-speed high-brightness objects based on a pulse array image sensor

We describe a method of optical flow extraction for high-speed high-brightness targets based on a pulse array image sensor(PAIS).PAIS is a retina-like image sensor with pixels triggered by light;it can convert light into a series of pulse intervals.This method can obtain optical flow from pulse data directly by accumulating continuous pulses.The triggered points can be used to filter redundant data when the target is brighter than the background.The method takes full advantage of the rapid response of PAIS to high-brightness targets.We applied this method to extract the optical flow of high-speed turntables with different background brightness,with the sensor model and actual data,respectively.Under the sampling condition of 2×10^(4) frames/s,the optical flow could be extracted from a high-speed turntable rotating at 1000 r/min.More than 90%of redundant points could be filtered by our method.Experimental results showed that the optical flow extraction algorithm based on pulse data can extract the optical flow information of high-brightness objects efficiently without the need to reconstruct images.

摆动阀式泥浆脉冲器电机输出特性及影响因素分析

摆动阀泥浆脉冲器本身可以产生较高频率的载波,成为高速泥浆脉冲传输的较好选择。由于工作时负载力矩复杂,影响因素众多,为电机输出特性研究带来较大困难。利用在井下工作时的动力学平衡方程,通过水循环实验方式测量得到摆动阀电机在最大转矩比电流控制方式下的位置角度和输出电流数据,进而计算井下工作时电机输出转矩和输出功率,并对其影响因素进行综合分析。结果表明,受惯性转矩、弹性转矩和动态水力转矩的影响,电机输出转矩在不同工作频段表现为不同特征;低频段时,电机输出转矩的变化幅度随载波频率的增大而减小,输出功率随载波频率的增大而缓慢增大;中低频段时,电机输出转矩和输出功率在该频段幅度变化较小,相对比较稳定;高频段时,电机输出转矩和输出功率均随频率的增大而快速增大。可以通过增大扭杆刚度系数和降低摆动阀转子轴系转动惯量的方式降低电机在高频段的输出,以保证电机在额定转矩和额定功率下可以控制摆动阀在井下实现高频快速的摆动,产生稳定高载波频率下的泥浆脉冲压力波形,实现高频载波的目的,为随钻测井数据的高速传输提供了保障。

随钻测井数据有损压缩算法改进探讨与应用

常规随钻测井一般采取泥浆脉冲传输技术,泥浆脉冲传输技术数据传输速率受限于自身的编码、解码及算法方式,已经难以满足日益增长的钻井工程数据传输需求,而常用于随钻测井的差分脉冲编码调制算法主要存在两个方面的缺陷:当原始数据变化剧烈时,部分解码数据误差较大,导致该部分解码数据不可信;另外,其压缩倍数较低。由于数据压缩技术有助于在保持泥浆脉冲传输技术硬件不变和信号传输速率不变的情况下有效提高其数据等效传输速率,文章对差分脉冲编码调制做了改进,将非均匀量化与均方根传播梯度下降法相结合,有效减小了解码数据的误差,并利用Huffman编码对非均匀量化编码结果做进一步压缩来提高压缩倍数。经过生产测试,结果表明:本文算法对电阻率数据和伽马数据的等效传输速率达到1.588 bit/s和1.782 bit/s,高于差分脉冲编码调制算法的1.164 bit/s和1.163 bit/s,压缩倍数分别达到了2.73倍和3.06倍,高于差分脉冲编码调制的2.00倍。同时,解码数据与采集数据信噪比分别达到27.97 dB和26.62 dB,高于差分脉冲编码调制的23.66 dB和19.15 dB。由此可见,本文改进算法在有效提升了差分脉冲编码调制的压缩倍数的同时减小了解码数据误差,对于提高泥浆脉冲传输技术在同样硬件条件情况下的等效传输速率具有重要意义。

YST-48R泥浆脉冲随钻测斜定向钻进技术的应用

YST-48R是一种正脉冲随钻测斜仪。它是在钻进施工过程中,地面设备通过实时接收泥浆脉冲随钻测斜数据,并利用井下单弯螺杆钻具,实现定向钻进的随钻定向钻进设备。YST-48R泥浆脉冲随钻测斜定向钻进技术在南黄海CSDP-2井扩孔改造钻进过程中的应用,有效地控制了钻孔轨迹,缩短了海上钻探施工周期,降低了施工成本,井斜、井径、全弯曲强度,井身质量满足设计要求。本文重点介绍了YST-48R泥浆脉冲随钻测斜定向钻进应用中的影响因素及技术措施,为今后海洋深部的扩孔作业钻探施工提供了技术支撑。

复杂顶板岩层大直径高位定向钻孔装备与技术

针对目前综放工作面复杂顶板岩层定向钻进成孔困难,卡钻、塌孔事故频发,以及大直径钻孔扩孔难度大,缺乏配套专用扩孔机具,高位定向钻孔成孔深度浅、钻进效率低、有效孔段少等问题,提出基于无线泥浆脉冲随钻测量系统、螺旋型钻具组合、多动力扩孔用双级双速钻头、煤矿井下护孔膨胀管等专用设备机具的复杂顶板岩层大直径高位定向钻孔技术,实现复杂顶板岩层成孔及扩孔的可靠性,改善工作面采空区瓦斯抽采的稳定性。实践表明:大直径高位定向钻孔单孔抽采纯量3.2 m^(3)/min,是常规定向钻孔的3倍,累计抽采瓦斯纯量1 300 m^(3),应用效果显著。

随钻测量系统的自适应消噪算法研究

在随钻测量(MWD)过程中,将井下数据传输到地面最常用的方法是泥浆脉冲遥测技术。钻井过程中包含众多噪声,其中泵噪声最为强烈,并且泵噪声的二次谐波频率接近有用信号,幅值也大于信息信号,这对地面接收信号产生强烈的干扰。如何消除泵噪声产生的干扰是准确并且及时获取井下信息的关键。通过分析已有算法的优缺点,提出一种改进的变步长LMS算法,该方法的基本原理在于利用信号间的相关特性强,噪声间的相关特性弱,并根据均值定理对步长进行调整,动态优化随钻测量系统泥浆信道噪声消除输出。仿真结果表明,该方法能够在强噪声的环境下成功地提取出有用信号,与其他几种消噪方法对比,该方法具有更快收敛速度。

泥浆脉冲遥传系统泵冲频率估计消噪方法设计

泵冲干扰作为泥浆脉冲随钻遥传系统中的主要干扰源,严重影响了遥传系统的通信质量。抑制泵冲干扰对提高整个遥传系统的接收性能具有重要意义。依靠泵冲频率这一参数,泵冲干扰抑制算法能实现更好的抑制效果。文章设计了一种倒谱辛格函数插值算法,直接从信号中估计泵冲信号的基频频率。实钻信号测试显示,与利用泵冲传感器信号计算的泵冲频率相比,倒谱辛格函数插值算法的估计误差达到了10-4量级,在实际工况中可以替代泵冲传感器。

基于傅立叶级数合成的自适应泵冲干扰消除模块设计

泵冲干扰是泥浆脉冲随钻遥传系统的主要干扰来源,该干扰源位于地面,强度远大于井下传输到地面的通信信号,对遥传系统的性能造成严重影响,因此抑制泵冲干扰对提高整个遥传系统的接收性能具有重要意义。文章设计了一种基于傅里叶级数合成的自适应泵冲干扰抑制方法。仿真结果表明,该算法能有效抑制泵冲干扰信号,同时也不会造成脉冲信号的波形失真。

煤矿井下随钻测量信号泥浆脉冲传输特性研究与试验

基于定向钻孔的地质保障技术可实现矿井致灾隐患的超前探查与治理,但受现有有线随钻测量定向钻进装备制约,存在信号传输干扰因素多、对定向钻具要求高、地层适应性差等不足,亟待开发矿用泥浆脉冲无线随钻测量系统。结合煤矿井下近水平定向钻孔施工特点,小泵量、低泵压和小直径条件下工作需要,建立了泥浆脉冲信号发生机构和水力通道模型,分析了泥浆脉冲信号传输速度、传输强度、衰减规律和传输影响因素等特性,给出了信号反射与透射、泥浆泵噪声干扰、孔内钻头旋转干扰和冲洗液流道阻塞等影响因素的针对性处理方法。分析结果表明,煤矿井下近水平定向钻进宜采用正脉冲方式进行信号传输;以清水作为冲洗液时信号传输速度为1 366.20~1 445.11 m/s;信号脉冲幅值可通过改变流道控制阀与孔板之间的间隙进行调整;信号传输衰减系数随冲洗液流量增大而线性增大,随钻杆柱内径增大而逐渐减小,当信号发射频率f>0.2 Hz后,衰减系数维持在0.126×10^-3 m^-1左右;采用煤矿井下常用钻杆,孔深1 500 m时孔口接收信号强度为孔内信号发射强度的73.74%~90.71%。现场试验表明,开发的矿用泥浆脉冲随钻测量系统信号传输误码率为3.2%,脉冲信号实际幅值一般小于理论计算幅值,但误差小于10%,最大实钻传输距离达到1 566 m,且具有更深的信号传输能力。

充气钻井随钻测量脉冲信号衰减规律

基于两相流体模型,考虑相界面的动量和能量交换、各相重力及管面黏性剪切力等封闭条件,建立充气钻井随钻测量(MWD)脉冲信号衰减的数学模型。利用小扰动理论求解数学模型,得到钻井液脉冲信号传播速度和衰减系数计算模型,模型计算结果与现场试验实测的脉冲信号衰减结果吻合较好。利用该模型计算并分析了钻井液脉冲信号衰减的影响因素,结果表明,持气率、系统压力和脉冲频率是影响钻井液脉冲信号衰减的重要因素。低持气率(0～5%)时钻井液脉冲信号的传播速度随持气率的增加而迅速降低,随着持气率的持续增加,其变化逐渐趋于平缓;而其衰减系数则随着持气率的增加逐渐增大,并在达到最大值之后开始下降。相同持气率时,高系统压力下钻井液脉冲信号具有更快的传播速度;低系统压力下钻井液脉冲信号的衰减系数随持气率增加上升速率更快。钻井液脉冲信号传播速度和衰减系数随脉冲频率的增加而逐渐增大,并都在脉冲频率大于100 Hz后逐渐趋于一个较高的稳定值。

泥浆脉冲随钻测量系统研究

介绍了泥浆脉冲随钻测量系统信号传输的3种基本工作方式:压力正脉冲、压力负脉冲和连续压力波。泥浆脉冲信号在传输过程中主要受钻探泵、井底动力机、泥浆中的气泡及活动钻具的干扰;钻井深度、泥浆中的气泡量、含砂量和泥浆类型对信号衰减有一定的影响。

基于PLM编码的泥浆脉冲信号提取算法研究

无线随钻测量(measurement while drilling,MWD)中泥浆脉冲信号的提取和正确识别是石油钻井施工中的一个关键技术,它决定着石油钻井过程中井眼轨迹是否正确。对泥浆脉冲信号进行了数值模拟,阐明了它的信号特征。针对PLM(pulse location management)编码的泥浆脉冲信号提取和识别问题,采用二次相关去噪算法,对泥浆脉冲信号的噪声去除进行了研究;在此基础上,运用局部特征和波形特征识别相结合算法,对PLM编码的泥浆脉冲信号位置进行了准确识别;为泥浆脉冲信号的提取和准确识别奠定了基础。最后现场试验结果表明:该算法简单实用,符合工程应用要求。